Recent years have seen the deployment of a variety of different access standards for use in wireless networks (e.g., GSM, CDMA, WCDMA, IEEE-801.16, etc.). However, the proliferation of wireless access standards has proven to be inconvenient and challenging for the manufacturers of wireless mobile stations (or terminal), such as cell phones, PDA devices, wireless laptops, and the like. End-user expectations of a ubiquitous network cannot be met with mobile stations that support only a subset of the possible standards.
In response, wireless mobile stations are transitioning to software-defined radio (SDR) architectures to provide common hardware platforms for multiple air interface technologies. The continual improvement of semiconductor process technology has enabled an increasingly greater percentage of the signal processing functions in a mobile station to be performed by reconfigurable hardware. The reconfigurable hardware may take one of several forms, including fixed functional blocks with customizable parameters and flexible interconnects. The reconfigurable hardware may be implemented, for example, in a field-programmable gate array (FPGA).
However, such reconfigurable hardware blocks have typically been used in the modem portion of the mobile station. The down-converter portion of the receiver generally still requires the use of hardware circuits that are adapted to particular modulation schemes. Thus, some multimode mobile stations implement several down-conversion circuits in order to operate under different air interface standards.
Therefore, there is a need in the art for an improved software-defined radio (SDR) mobile station capable of operating under different air interface standards. In particular, there is a need for an improved SDR mobile station that implements a reconfigurable multi-mode digital down-converter.